Laundry apparatus



INVENTOR EARL K. CLARK BY Q ATTORNEY COOL/N6 TIME E K CLARK LAUNDRY APPARATUS Filed Oct. 18. 1949 Dec. 16, 1952 B/METAL 68 Patented Dec. 16, 1952 LAUNDRY APPARATUS Earl K. Clark, Mansfield, Ohio, assignor to Westinghouse Electric Cor Pa., a corporation of poration, East Pittsburgh, Pennsylvania Application October 18, 1949, Serial No. 122,104

1 Claim.

My invention relates to apparatus for drying clothes or the like and has for an object to pro vide improved apparatus of this kind.

Further objects of my invention are to expedite the heating of the air translated to the drying chamber of an electrically heated clothes dryer of the domestic type when the dryer is started from a cold condition; to maintain the temperature of the heated air supplied to said drying chamber substantially constant regardless of fluctuations of voltage impressed on the heaters of the dryer and to compensate for changes in temperature of the ambient atmosphere.

In practicing my invention, I provide a drying chamber in which clothes are preferably tumbled during the drying treatment, which chamber is supplied with air heated electrically by a pair of heaters. The heaters are energized by manually closing a master switch and deenergized when the temperature of the air in the drying chamber increases to a predetermined value prevailing when the clothes are dry. The heaters which have different capacities are preferably energized in parallel and the smaller heater is controlled by a thermostat responsive to the temperature of the heated air as it leaves the heaters and prior to its admission to the drying chamber, the arrangement being such that said heated air is maintained at a predetermined mean temperature. When started from a cold condition, both heaters are energized for rapidly raising the temperature of the air admitted to the drying chamber. The large heater is continuously energized and the smaller heater intermittently energized to maintain the temperature of the air constant. When operated at a lower than normal voltage, the smaller heater is energized for longer periods than when the voltage is normal. With normal voltage prevailing, the periods of energization of the smaller heater are relatively short. Also, the periods of energization of the smaller heater are longer when the ambient atmosphere is relatively cool and of shorter duration when the ambient atmosphere is relatively warm.

The foregoing and other objects are effected by my invention as will be apparent from the following description and claim taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a vertical sectional view of one form of domestic dryer constructed and arranged in accordance with my invention;

Fig. 2 is a diagram of the electrical connections for the dryer shown in Fig. 1; and

Figs. 3 and 4 are curves illustrating temperature conditions within the dryer during a cycle of operation.

Reference will now be had to the drawing wherein I have elected to show my invention applied to a domestic clothes dryer of the type including an outer casing structure It! having a general cylindrical baffle ll secured therein and enclosing a drying chamber l2. A basket structure i3 is rotatably supported within the drying chamber [2 and includes a shaft 14 suitably journaled in the casing I0. The basket structure l3 includes a side wall [5 which is substantially perforate throughout its extent, a few of the perforations being indicated at 16, and a plurality of vanes l1 extending radially inwardly from the side wall IS. The basket I 3 is driven by a pulley l8 belted, as shown at [9, to a pulley 2i driven by the shaft 22 of a conventional electric motor 23. It will be understood that, as the basket I3 is rotated, fabrics contained therein are elevated and dropped by the rotating vane [1.

Air for drying the fabrics is translated through the drying chamber l2 by a blower 24, the rotating element 25 of which is directly driven by the shaft 22. Air from the ambient atmosphere enters the casing it) through an opening indicated at 26 and passes through an opening 21 formed in the blower housing 24 to be driven by the runner 25 through a duct structure 28 to the drying chamber E2. The downstream end of the duct structure 28 is provided with an upwardly extended portion 29 which is fixed to the baffle H. The air translated by the blower is heated by a plurality of electric heaters 3i and 32 which, for the sake of clearness and brevity, are diagrammatically shown. It will be understood that the heaters 3| and 32 may be of any wellunderstood construction and supported within the duct 28 in any suitable manner. Preferably, the heaters 31 and 32 are coiled lengths of bare heater wire which are directly contacted by the air as it passes through the duct 28. As described hereinafter, the heater 3| operates throughout the drying portion of the cycle continuously and will be referred to as the primary heater while the heater 32 is intermittently operated and will be referred to as the secondary heater.

The heated air entering the drying chamber l2 passes through the numerous perforations 16 to the interior of the basket I3 where it contacts the tumbling fabrics and, due to its high capacity for vaporizing water contained in the clothes, effects the drying of the clothes. The air and to the bias of th 55.

moisture entrained therein passes through an outlet duct 33 to the ambient atmosphere. Energization of the electric motor 23 and the heaters 3! and 32 is under control of a primary control element generally indicated at 35 and described hereinafter.

The primary control device 34 is manually actuated to initiate energizaticn of the heaters 3i and 32 and operation of the electric motor 23. The device 33 is thermostatically operated to terminate energization of the heaters 3i and 32 at the conclusion of the drying cycle. The control device 55 preferably includes a main 2-pole switching element 35, one pole of which is. defined by contacts 36 and 31 and a bridging member 35. The other pole of the switching element 35 is defined by stationary contacts 39 and ll and the movable bridging member 42. The movable bridging members 38 and :2 are insulatedly carried by a movable resilient switch arm 43 pivotally supported by a fixed pivot 55. At the upper end of the switch arm 53, a conventional U- shaped snap-over compression spring 45 is provided to effect snap-acting movement of the switch arm 53 in both closing and opening directions thereof. The U-shaped spring 55 is compressed between the end of the switch arm 33 and a fixed knife-edge, indicated at 45.

The switch arm 43 is moved to a switch closed position from the position shown in the drawing by a manually actuated handle 47 when moved to the right as viewed in Fig. 2. The handle is carried by a rod 48 having a pair of spaced shoulders 59 and 5| formed thereon and arranged on opposite sides of an extension 52 of the switch arm 43. The manually actuated handle 61 also operates to close a single pole switch, indicated at 53 and including a fixed contact 55 and a movable contact 55, the latter being carried by a spring support 55 which biases the movable contact 55 to a switch open position, as shown in the drawing. A cam 51 carried by the rod 513 is engageable with the spring arm 5'5 for closing the contacts 54 and 55. Opening of the main switch 35 at the conclusion of the drying cycle is effected by a thermostatic element including a bellows 58 and a tube 59 communicating therewith and terminating in a thermostatic bulb 6|, which bellows and tube are filled with an expansible liquid. As shown in Fig. l, the bulb Si is fixed to the baffie l l at a location thereof which closely follows the temperature of the air within the drying chamber [2.

In actuating the primary control device 34 to its active position, the handle 41 is moved to the right, as viewed in Fig. 2. The first stage of movement of handle 41 causes the cam 5'5 to force the switch 53 to its closed position and to engage the shoulder 5| with the projection 52. Continued movement of the handle 4'! through a secsta e swin s the arm counterclockwise in opposition to the bias of the over center spring 45 and closing of the main switch 35 is carried out with snap action. As the bellows expands during heating of the bulb 5|, the arm 43 is deflected in clockwise direction in opposition When a predetermined temperature of the bulb 6! is attained, the spring 55 moves over center with snap action and arm 43 operates to open main swtich 35. During this movement of arm 43, the projection 52, now in engagement with shoulder 5i, moves cam 51 and handle 41 to the left but not suffici ntly to open switch 53. Opening of the switch 53 is efiect'ed only by further movement of handle ii and cam 57 to the left, manually, or to the position shown in the drawing. Opening of the main switch 35 and the single pole switch 53 may be effected at any time by manually moving the handle 41 to the left through its complete range of movement. Such movement of handle 41 would first disengage shoulder 5| from projection 52 and engages shoulder 55 with the projection 52. The cam would still engage the spring 55 for retaining the single pole switch 53 closed. Further movement of the handle 5'! to the left, or to the position shown in Fig. 2, will open both switches 35 and 53.

The source of power for the heaters 81 and 52 and for the electric motor 23 is preferably defined by an Edison 3-wire circuit having line conductors L1, L2, and N, the voltage across conductors L1 and L2 being 230 volts and the voltage between either L1 and L2 and the neutral conductor N being 115 volts. As clearly shown, the conductor L1 is directly connected to the fixed contact 35 and the conductor L2 directly connected to the fixed contact 55. The neutral conductor N is directly connected to one side of the motor 23. The fixed contact 31 connects, by means of a conductor 52, with one terminal of the primary heating element 3|, the opposite terminal of which is connected by conductor 63 with the fixed contact 39. One terminal of the motor 23 is connected by means of a conductor 55 with the fixed contact 39. As shown, the fixed contact A! is connected by means of a conductor 65 with the movable contact 55 of switch 53. In order to provide for continued running of the motor 25 after the main switch 35 has opened, as described hereinafter, a shunting conductor 66 is provided which extends from the conductor 54 to the conductor 65 and, therefore, shunts the fixed contacts 39 and 41 of the main switch 35.

According to my invention, the secondary heater 32 is directly connected in parallel with the primary heater 3! by means of conductors 6i and 58 and is, therefore, under control of the main switch 35. The secondary heater 32 is also controlled, according to my invention, by a thermostat, indicated at 59 and including a bimetal element 1| which, when relatively cool, bridges contacts i2, the latter being connected in series in the conductor 68. When heated to a predetermined high temperature, as described hereinafter, the bimetal element H snaps to an open position and disengages the contacts 52.

A second thermostat, indicated at '53, includes a bimetal element M which when heated to a predetermined temperature bridges contacts connected in series in the conductor 55, for a purpose to be described. A safety thermostat 36 including a bimetal element T! which, when closed, bridges contacts 18 connected in series in the conductor 63. The thermostat T5 is normally closed and opens its contacts 78 only when an abnormal temperature obtains in the duct 25 for any reason. All or the thermostats 68, i3 and 15 are preferably located in the duct 23 on the downstream side of the heaters 3i and 32 where they reflect the temperature or the heated air being discharged to the drying chamber l2.

In operating the dryer described up to the present, the clothes to be dried are deposited in the basket 13 through a suitable access opening, not shown. The handle 47 is then withdrawn or moved to the right from the position shown in Fig. 2 for closing both switches 35 and 53, as described heretofore. This operation of the primary control element 34 energizes both heaters 3| and 32 and the motor 23 is energized to initiate the circulation of air to the drying chamber 12. The circuit for the heaters 31 may be traced from the line conductor L1 through the bridged contacts 36 and 37, the conductor 62, the main heating element 3!, the conductor B3 and safety thermostat l6, bridged contacts 39 and 4|, the conductor 65 and switch 53 to the line conductor L2. As the secondary heating element 32 is directly connected in parallel through the closed thermostat 69 with the primary heating element 3!, the secondary heating element 32 is also energized. The circuit for the electric motor 23 may be traced from the line conductor L2 through switch 53, conductor 65, the bridged contacts 30 and 5|, conductor 04 and motor 23 to the conductor N.

The temperature of the air passed in heatexchange relation with the heaters 3! and 32 progressively increases during the early stage of the heating cycle. During this heating up portlon-of the cycle, the bimetal 14 of the thermostat 13 operates at a temperature of about 160 F. to bridge the contacts 15 and, therefore, close the shunt circuit defined by the conductor 33. At the moment, this is of no importance as the shunted contacts 33 and 4| are already bridged by the member 42. The purpose of closing this shunt circuit is to maintain operation of the motor 23 after the two pole switch 35 has opened at the end of the drying cycle, as described hereinafter. Heating of the air continues until a temperature of approximately 300 F. is attained, at which time, the thermostatic element H snaps to its open position for deenergizing the secondary heating element 32. Subsequent cooling of the air in the duct 28 will again close the thermostat 59, this operation occurring at a temperature of about 280 F. The thermostat 63 will then function to energize and. deenergize the secondary heating element 32 to maintain a mean air temperature of approximately 290 as it enters the drying chamber I2.

Assuming the secondary heating element has a capacity of 1400 watts and the primary heating element 3! a capacity of 3400 watts, when energized at 230 volts, 4800 watts of energy is dissipated during the heating up portion of the cycle. During the early stage of the drying cycle, a substantial portion of the energy in the heated air stream is converted to latent heat of vaporization so that the temperature rise of the air in the drying chamber is relatively small. As the fabrics become dried, less energy is converted to latent heat and more to sensible heat so that the temperature of the air in the drying chamber l2 progressively increases. When the temperature of the air in the drying chamber l2 attains a value of approximately 200 F., the clothes are substantially dry. During the period of drying of the fabrics, the bellows 58 expands and deforms the resilient arm E 3 and, when the temperature of the air in the chamber has attained a temperature of 200 F., the main arm 43 snaps to the position shown in the drawing for opening the two pole switch 35 and, therefore, deenergizing both heaters. During this operation of the switch element 34, the rod 68 is moved to the left by the projection 52 which now engages the shoulder 5|. As set forth heretofore, this movement of the rod 48 is not sufficient to open the switch 53 as the cam 51 still engages the switch arm 56. Accordingly, operation of the motor 23 continues for the circulation of cool air as the motor 23 is energized heaters 3 I through the shunt circuit defined by the condoctor 65 and the switch 53. Operation of the motor 23 is terminated by the opening of the shunt circuit 66 when the temperature of the bimetal 14 has been reduced to a value slightly below F. The operation of the motor 23 can be terminated at any time however by manually moving the handle 4'! completely to the left as viewed in the drawing.

The temperature at which the bellows 58 operates to open the two switches 35 may be varied by a temperature adjusting knob BI and an abutment 82 which is threaded in the resilient arm #3. Accordingly, the fabrics may be completely dried or damp dried depending upon the adjustment of the handle 8| all of which is well understood.

From the foregoing, it will be apparent that the heaters 3i and 32 are cycled between 4800 watts and 3400 watt-s for heating the air, in the example cited, when energized at a normal potential of 230 volts. The two curves shown in Figs. 3 and 4. show temperatures plotted against time, Fig. 3 illustrating conditions when a relatively high potential of 245 volts is impressed on conductors L1 and L2 and Fig. 4 showing conditions when a low potential of 215 volts prevails. The portion A of the curves illustrates the initial heating period of the input air passing over the thermostat 69. The point B represents 300 F. in the example cited and the point 0 280 F. In Fig. 3, the input air is heated by the elements 3! and 32 which consume 5440 watts and the air cools at a slow rate with 3850 watts being consumed after the thermostat 69 opens. In Fig, 4 the input air is heated at a lower rate of 4180 watts and the air cools with the primary heater dissipating 2960 watts.

In one form of dryer which I have constructed, the input air, when heated by 4000 watts of dissipated energy, is maintained substantially at its proper mean temperature of 290 F. This wattage is dissipated by the primary heater 3| when energized at 250 volts and by the combined and 32 when energized at 210 volts. At these two voltages, the thermostat 69 would not be called upon to operate and the temperature curve, after the initial preheating period, would be substantially flat. Accordingly, this dryer will maintain the proper temperature of input air when operated between 210 and 250 volts. Beyond these voltages compensation ceases, but abnormal voltages beyond this range are infrequently met on lines of present day utilities.

From the foregoing description it will be apparent that I have provided an improved clothes dryer of the domestic type wherein the temperature of the air admitted to the drying chamber is maintained at a substantially constant value by a pair of heaters, one of which is continuously energized during heating periods and the other of which is controlled in accordance with the temperature of the air leaving the heaters. With this arrangement, the temperature of the admitted air is maintained at a fixed value regardless of variations in voltage within a relatively wide range. Furthermore, the initial preheating of the air is expedited and compensation for changes in temperature of the ambient air is carried out. In this connection, with a relatively high ambient temperature, the periods of energization of the secondary heater are relatively short and, conversely, with a lower ambient temperature, the periods of energization of the secondary are relatively long.

While I have shown the invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What I claimis:

In a clothes dryer, the combination of means defining a drying chamber, a duct structure for conveying air to the drying chamber, means for translating air through the duct structure, primary and secondary electric heaters connected in parallel and disposed within said duct structure for heating air translated therethrough, a pair of line conductors defining a source of electric power for said heaters, a master switch controlling said heaters and-manually movable to a closed position, said switch when closed connecting said heaters directly across said line concluctors and subjecting said heaters to the full voltage of, said source of power, means responsive to a predetermined high temperature of the air in the drying chamber for opening the master switch, and a thermostatically operated switch responsive to the temperature of the heated air in said duct structure and connected in series with said secondary heater for controlling energization thereof, said thermostatically operated switch effecting energization and deenergization of said secondary heater in response, respectively, to predetermined low and high temperatures of the heated air.

EARL K. CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

